Circuit Description

WARNING: This page is about a different car, the 2000 Isuzu Hombre. However, it is still accessible from the selected car via links, so may be relevant.

Vehicle Control Module (VCM) controls idle speed with an Idle Air Control (IAC) valve to a calculated RPM based on sensor inputs and actual engine RPM. VCM moves IAC valve in or out to vary amount of airflow into intake manifold and thus decrease or increase idle RPM.

VCM commands IAC in counts. A higher count, allows more air to by-pass throttle plate (higher idle).

Conditions required to set DTC are:

No ECT, MAP, TP or VSS DTCs set.
ECT greater than 122°F (50°C).
IAT greater than -13°F (-25°C).
BARO greater than 70 kPa.
Vehicle speed less than 2 MPH.
System voltage is 10-16 volts.
TP is less than one percent.
Engine running longer than 30 seconds.
Conditions met for more than 3 seconds.